The oleuropein and demethyl-oleuropein glucosides present in high quantities in olive drupe are the main cause of bacteriostatic and bactericidal activity of the olive mill wastewater. The use of microrganisms to reduce or remove the by-products phenols content is one of the most interesting solution to optimize the fermentation processes that underlie the biogas generation. Biological oleuropenolytic activity is expressed through the action of two key enzymes: -glucosidase and esterase. In the present work we studied the oleuropeinolytic activity of three strains of Lactobacillus plantarum from the Collection of Microrganisms of CRA-OLI (Lactobacillus plantarum B28, L. plantarum B51 e L. plantarum B124; www.colmia.it), through a) the presence of the gene bglH encoding -glucosidase by PCR b) -glucosidase and esterase activities by colorimetric assay c) oleuropein degradation tests by HPLC hydroxytyrosol detection (method COI/T.20/Doc. No 29. November 2009) d) microorganisms growth at different pH to test fermentative ability in highly acidic, neutral to strongly basic environment, in order to respond optimally to different starting biomass and e) microorganisms growth at different temperatures to test fermentative ability during the first phase of process (T < 15°C of the starting biomass stored outdoors during winter) or during the anaerobic digestion (T > 40°C of the biomass in the digester).The growth of B28, B51, and B124 L. plantarum strains was drasticallv reduced onlv below pH 4 and at T < 30°C. All strains are potentially oleuropeinolytic because have the gene encoding for -glucosidase, but only B51 after 24h degrades 82 % of oleuropein added to MRS broth as fermentative substrate unlike B28 e B124 (about 67 %). In the preliminary test of degradation of phenols, the OMW utilised in the trials came from an olive mill equipped with a 2-phases and half centrifugal decanter (cvs Leccino and Carolea). The OMW chemical characteristics were: pH 5.14; oil content 4.07 g/L; organic substance 95.07 g/100g dry matter; reducing sugars 1.97 g/100 ml OMW; total polyphenols 5667 expressed as caffeic ac. mg/L OMW. The OMW fermentation plot was carried out in a glass fermenter 10L capacity (LiFlus GX II, Biotron) at 30°C for two weeks and an inoculum of L. plantarum B51 108 CFU/ml was used. Uninoculated OMW was used as control test at the same conditions. The chromatograms obtained show the biodegradation capability of the strain used. Further studies are in progress in order to use such bacteria for OMW treatments.
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